Monday, 30 August 2010

Shetland tattie dreams

Shetland Black

A few years ago I bought some Shetland Black potatoes from Waitrose and they were very tasty. They were intriguing looking things … small, elongated and a muted shiny black with pale corky spots on the skin and a 'netted' surface. Inside they had a distinctive purple ring set into the pale yellow flesh. I saved a few and planted them. They grew pretty well, so I wrote a review of them.

A short while after writing the review, I had a message from Jon who lives in Shetland. Did I know, he asked, that the Shetland Black sold in Waitrose is not the same as the Shetland Black grown by the crofters on the islands? Well no, I didn't. And when he kindly offered to send me a sample of the "real thing" it was not something I was going to turn down.

A box duly arrived with a generous stash of "real" Shetland Black tubers, and I saw what he meant. They are certainly similar to the commercial ones, in that they are black-skinned and yellow-fleshed with a trace of purple inside. But they are rounder in shape, with deeper eyes. The flesh is a stronger yellow, and instead of having a simple purple vascular ring, the purple is more diffuse and spreads into the flesh, although it still has about the same amount of purple overall. The skin is a softer charcoal black, with a slight coarseness and a few pale speckles but none of the distinctive 'corky spots' or netting of the commercial type. When the tubers sprout, the sprouts are purple rather than the glossy black of the commercial version. It is, as Jon put it, "subtly yet profoundly different".

The Shetland Black potatoes from Shetland, as grown by Jon.

And while I find the commercial Shetland Black very well flavoured, the flavour of the local version is really outstanding. It has an exceptionally rich, strong, old-fashioned flavour with no bitterness in the skin, and the flesh is dense and smooth. The flavour is excellent when boiled and the potato holds together well without breaking up … if the outer skin is undamaged it keeps its purple colour. It also makes nice roasties, albeit rather dense ones with a thick skin. But then I guess that isn't an issue if you peel them … it's just one of my personal funny little ways that I never, ever peel potatoes.

Interestingly, Alan Romans mentions in his Potato Book that the version of Shetland Black conserved in the National Collection is considered by many Shetlanders not to be "right", and the authentic local version is described as larger and rounder with deeper eyes - exactly what I have here. Jon tells me that even within Shetland there are several more variants, some with a paler skin colour.

Naturally I was intrigued to see how the plants compared to the ones I'd already reviewed.

Standard Shetland Black on the left, "real" Shetland Black on the right.

Darker skin, yellower flesh, rounder tubers. The flowers do look fairly similar, but the difference not visible in this picture is that the one on the left is a rarity! This is the only decent specimen I've ever seen on the standard Shetland Black, it's usually a saggy specimen with wonky anthers or none at all. Whereas the one on the right flowers profusely.

"Real" Shetland Black produced very large voluptuous plants with big, dark green leaves, again quite different from the standard Shetland Black which tends towards the straggly end of the spectrum. To my delight, its flowering habits are also very different. It produces masses of blooms, large, elegant and mauve-petalled, borne over a long season. The real delight for me though is that it is a natural berry setter, loading itself up with large purple and green mottled fruits. In fact it's a potato breeder's dream. It has fertile pollen which can be used to pollinate other varieties and make hybrids. It will also accept pollen from other potato varieties to make more hybrids. And it is self-fertile, so I can also use it to pollinate its own flowers and reshuffle the contents of its own genepool without crossing it with anything else. To put this in perspective, the number of cultivated potato varieties which are fully male/female fertile is thought to be around 4 or 5%. Among the 95% of others which have compromised fertility is the commercial Shetland Black, which rarely flowers at all, and when it does its rather half-arsed mauve and white blossoms quickly drop off without producing any berries.

So I have been using "real" Shetland Black as both a male and female parent in my breeding programme this year. This is a good thing for me, because it brings interest and diversity. But it's also a good thing for Shetland Black, because one of the surest ways to conserve heritage vegetables is to pass their genes forward into new recombinations. Next year I will be able to sample such joys as Shetland Black x Salad Blue, Shetland Black x [Mandel x John Tom Kaighin], Highland Burgundy Red x Shetland Black, Marfona x Shetland Black, Congo x Shetland Black and possibly others. Plus of course the self-pollinated Shetland Black x Shetland Black, which will be interesting in itself. Potatoes can show a trace of inbreeding depression from self-pollination because nature really made them to be an outbreeder and they're not supposed to be self-fertile (the mechanism for preventing it got screwed up when they acquired their doubled genome). But in practice, self-pollinated seeds often produce really sturdy plants, just as vigorous as a hybrid would be. There's enough genetic diversity in the potato's tetraploid makeup to allow for a healthy bit of internal reshuffling.

My guess, and I must emphasise that it is only a guess, is that the commercially available Shetland Black could be derived from this local version, as the high fertility makes it very easy to save and share seed from it, either self-pollinated (in which case it's a simple reshuffling of the same genetic material) or a cross with something else. The reason I think the local one is probably the older of the two is because of its deep eyes. Shallow-eyed potatoes are a relatively modern innovation, prized for ease of peeling, and although the deep eyes of the local variety are not proof of antiquity, the shallow eyes of the commercial version certainly suggest a more modern origin. And also, the commercial Shetland Black has such low fertility it would be extremely difficult to breed anything from it.

The crop of Shetland Black I grew this year produced tubers somewhat smaller than the ones Jon originally sent me, but made up for it by producing absolutely masses of them … the yield overall was high. My guess is that they will adapt within a year or two and start producing the full size ones. On the whole, the plants seem to be very happy growing down here.

Part of what I wanted to find out was how well the Shetland tatties would adapt to being grown this far south. To any Americans and Australians reading this, the British Isles probably seem very small, and relatively speaking they are, but all the same there's a huge difference between the clement lush greenery of south-west England and the rocky windblustered Shetlands so many miles out in the Atlantic Ocean, far beyond the northernmost tip of Scotland. Shetland potatoes are adapted to thin peaty soil overlaid on solid rock, which is naturally acidic and supports a very different range of plants from the deep sandy loam of Cheltenham, which is naturally infused with limestone.

At one time Shetland had quite a range of unique local potatoes, bred for the particular needs of the soil and climate and maintained through many generations, helped no doubt by the extreme remoteness of this group of islands. Potatoes are known to have arrived in Shetland in the 18th century and formed a very major part of the islanders' diet. In the past, whaling boats from Shetland travelled as far as South America, where potatoes are native, and it's just possible that they picked up some spuds on their travels which differed from those already doing the rounds in England and mainland Scotland. Unfortunately many of these unique local varieties are now lost. Jon says that many older people on the island remember a red potato called Marrister Red which appears to have vanished, and also one called Yell Blue. He was, however, able to send me a sample of a rare and precious survivor among traditional Shetland tatties, which hails from the really tiny island of Foula.

Foula Red

Foula is a fascinating place with a beautiful landscape - the islanders have a truly lovely website devoted to its heritage. It measures only three and a half miles by two and a half miles - you could probably walk its entire length in an hour, if it wasn't for the spectacularly steep slopes - and a population of around thirty people. It has the highest sheer sea cliffs in Britain, plunging straight down more than 1000ft. It has prehistoric stone rings and scattered shipwrecks. And remarkably for such a tiny and sparsely populated island, it has its own sheep and its own potato.

It's difficult to explain just how rugged this potato has to be in order to survive as a viable food crop in Foula. Shetland weather can be very extreme. When in 1936 the island became the setting for a film starring John Laurie (later of Dad's Army fame), the camera crew were astounded by the sight of water in a mill loch being blown 300ft into the air by the force of the wind. But when they tried to film this spectacle they found the wind so strong neither they nor the camera could stand up in it, and they ended up having to crawl back to base on their hands and knees. Magical and inspiring the landscape may be, but this is not a good environment for growing vegetables. The traditional solution to this problem is to grow them in plantie crubs - small circular enclosures made of stones and turf, where the walls are high enough to prevent the plants from being blasted away and a decent layer of soil can be maintained to supplement the thin squishy peat which constitutes the island's natural topsoil.

The Foula Red potato is rounded, sometimes slightly kidney-shaped, with very shallow eyes and a pink-red skin, having a slightly rough matt surface. The flesh inside is a pale yellow, and it doesn't have internal colouring like its Black counterpart. The sprouts are pale pink and the plants grow into fairly large sprawling specimens with unusually large and flat leaves, dark green and with a rosy blush on the leaf stems.

It does have one major drawback though. It is almost laughably low yielding. The spuds are a decent size, but four or five tubers per plant is as much as they can offer. They look so promising as you grub around the base of the plant and unearth the first voluptuous brick-red tuber, since the largest one is usually at the top. And so you eagerly scrabble through the earth to find the rest of them and … er … there aren't any.

The crofter who gave Jon the tubers said that it's traditionally a low-yielding variety and it's quite normal to get such a miniscule crop. The reason it was worth cultivating was that it showed better blight resistance than other varieties grown on the islands, and therefore ensured at least some harvest during bad blight years … an important consideration in a community traditionally dependent on its own food production.

Foula Red is a natural survivor. This plant had its stem damaged by snails, and responded by making stem-borne tubers.

Well, when I grew my Foula Reds for the first time in 2009 they came up happily enough and made fine plants, but were almost immediately struck down by blight! Really complete, devastating blight which killed them in a couple of days. What was most strange was that they were the only plants in the garden to succumb … all my other potatoes were fine. This doesn't mean, however, that Foula Red has been wrongly labelled as blight resistant. The fact is, blight is an incredibly fast-mutating fungal disease and even the most resilient potatoes become vulnerable over time. Since the arrival in Europe of two mating types of blight which quickly got loved up, the version of the disease we are currently blighted with is a new supersonic strain which raises merry hell and simply didn't exist here before the late 1970s. Foula Red may well have had good blight resistance, but the goalposts have moved.

So anyway, fearing I'd lost this precious rare potato, I searched the soil and found a few tiny baby tubers that had just started to form. They were barely bigger than peas. But I kept them safe over winter, and in spring they sprouted, and remarkably, have given me six fine healthy plants in 2010. And this time, they have survived long enough to give me their proud harvest of a couple of tubers each.

My English-grown Foula Reds made it to full size, and are as big as the ones Jon originally sent me. The one thing that is different though is the skin texture. As you can see, the big one in the photo has got the same smooth roughness of the originals but many of the others have a crazed surface where the outer skin is sloughing off, very rough to the touch. I assume this is down to soil differences, though I'm not expert enough in potato behaviour to know what causes it.

And having sampled the taste of them for the first time, I found the flavour really excellent. It's quite similar to Shetland Black in old-fashioned richness, but it's milder and sweeter. The texture is lovely, dense but refined. Worth growing as a delicacy.

It might seem a bit odd to want to keep growing a variety which is both low-yielding and blight susceptible, especially as it's also quite slow maturing which makes the blight more of an issue. But I think something has been lost in the modern culture of wanting to maximise everything. Potato breeding focuses primarily towards larger yields, which is great, but there is still a kind of magic in only having enough to make an occasional treat. If the Foula Reds only produce enough potatoes for a couple of meals, fine - those meals are a special event. And there's also the fact that it's a rare type with no commercial potential and very limited distribution, which creates more of an imperative to take care of it. Local, heritage and landrace varieties shouldn't be judged by the same criteria as modern commercial ones. Foula Red may not win any accolades for its bounty or disease resistance, but it survives on an island with boggy soil and 100mph gales. Who knows when those genes for climate resilience might come in useful, or how important they might one day be for our future food security?

Something else I noticed, unless it's just the shock of adapting to a new climate: Foula Red is a late bloomer. Most potatoes start to flower around the time they set tubers, and Foula Red duly produced a couple of apologetic looking bud clusters which promptly aborted before they even thought about opening. Then it made its tubers, and then … when the tubers were already full size and the season was nearly over, it began to flower properly. Not all the plants produced flowers, only the two biggest ones, but they were a lovely surprise. Very pretty, elegant flowers in a light mauve with bright yellow anthers. They were a joy to behold. More for the sake of scientific study than any serious hope of finding anything, I plucked an anther and prodded it to see if there was any pollen in it. There were veritable plumes of it! Masses and masses of pollen. In fact, left to dehisce naturally it was dumping big white splodges of powder on the leaves underneath. It's pretty rare for potatoes to produce pollen in that kind of abundance. Excitedly, I dabbed some of it on the pistils of its own flowers, and on one or two other potatoes which were still flowering, which wasn't many at that late stage in the season. To my delight, every dabbing resulted in a plump healthy berry. So Foula Red, as well as Shetland Black, belongs with the 4% or so of cultivated potatoes which have complete male/female fertility.

Foula Red flowers

This is really good news. As with Shetland Black, it will allow me to make new varieties from it (if I can find a partner for it which flowers at the same time). But more importantly, it is a huge help in ensuring the variety's future survival. Tubers have a finite lifespan, and any variety which can't produce its own seed (i.e. most of them) is difficult to maintain long term. Foula Red's ability to produce TPS, either by itself or by contributing its genes elsewhere, will enable it to regenerate. Of course being tetraploid (I assume Foula Red is tetraploid) the seeds from self-pollinations will not come "true" to the variety in every detail but they are nevertheless a recombination of the same genes. And who knows, they might even throw up a variant with decent yields. Ha.

So thank you very much Jon. And all credit to the crofters of the Shetland Isles who know a good tattie when they see one.

Thanks Jeremy. I love Highland Burgundy Red. The striking colour comes from its unusually high levels of petunidin, a different type of anthocyanin from most other coloured potatoes. I had thought it incapable of producing TPS, but was delighted to find that it has both male and female fertility if given a sufficiently persistent prodding.

Just out of interest, what methods did you use to keep your tubers virus free? I know many people swear by the DIY meristem culture technique ... any nuggets of wisdom you could share?

Kath, yes the drought was a hindrance to some of mine too. But I have now tasted two of my Salad Blue OP offspring and they were both excellent.

I don't know the Isles, apart from Skye, but having been blasted off my feet and rolled along the ground by a gust on Cairn Gorm, I can well believe the story about water being blown hundreds of feet into the air!

Looking at Mal's comment, I was thinking that the round shape and deep eyes reminded me of Epicure. Such a shame that the supermarkets don't champion the best tasting potato but are only really interested in attractive, smooth skinned varieties!

They look good. I remember we grew seedlings of Shetland Black at Ryton one year, but can't say which version it was. Would you be interested in some other unusual spuds I've just laid my hands on? More details will be appearing on my blog soon. I fear for their safety in this thoroughly Blue 13/ Pink 6 spot. Mersitem tip culture isn't hard to do if you have a pressure cooker, sugar, agar and alcohol. I know you've got a scalpel - but you might need to change the blade....

Robert - I was once blown flat on the ground and had to crawl to safety by slithering along on my belly, digging my fingers into the grass and seriously fearing for my life. But it wasn't in the north of Scotland ... it was on the top of Glastonbury Tor when I climbed it one full-mooned winter's night. The weather was fine until I got to the top. I guess I was struck by the faery blasts of Avalon.

Mal and Matron - interesting to know of the Epicure similarity. It could be related somewhere along the line.

Soilman - yes you are welcome to some Shetland Black seeds - I'm going to have more than I can use in a lifetime. Self-pollinated ones or hybrids with other things ... whatever you'd like. Vitelotte is one I was trying to get this year but it was sold out ... so yes, I would be interested.

Owen - you'll have to teach me the meristem tip culture method. I don't have a pressure cooker but I'm guessing that getting one would still be cheaper than sending off my spuds to a laboratory for a pro job. Oooh ... the prospect of more unusual spuds interests me strangely. Thank you.

You say that Highland Burgundy Red does not produce berries. I have just seen a planting of supposedly Highland Burgundy Red and most of the flowers have fallen off, however, one berry has appeared. Something succeeded in pollinating it.I shall harvest it, and see how many seeds are inside, and send you some if you wish.

i stayed on foula for 6 weeks when a student great place but stormy even in summer so much so they park the boats in a boatpark onland. not tried the potatoes though. does anyone know where I could get some to grow for next year

Is AlanRomans.com defunct as well? SO many of the interesting suppliers you mention seem not to exist any longer. Would you please consider updating your supplier list? It is very sad to keep coming up blank time and again, seeking the names of suppliers you mention.

Daughter of the Soil

About me

My name is Rebsie Fairholm and I breed vegetables for fun in my organic suburban garden in Cheltenham, England. I have a special love of heritage varieties, so that's what I use in most of my experiments. On this blog you'll find lots of information about heritage veg, basic genetics, hand pollination and seed-saving.

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